Powerline adapters are dependent on the layout and condition of your home' electrical circuits.
However, you should be able to narrow down the possibilities:
Do you have another known working (at speed) computer that you can connect in place of your computer? Determine if the slower speed remains or changes one way or another.
Were you originally using wireless on your pc before going wired via the powerline adapters?
If so, ensure that the pc's wireless adapter is disabled. Only the wired network adapter should be enabled.
Double check the wired network adapter's configuration settings.
Try another known working, at speed, ethernet cable between pc and powerline adapter.
Do likewise on the other end; router to powerline adapter.